elpa_generalized_eigenvalues(3)

1elpa_generalized_eigenvaluesL(i3b)rary Functions Maneulapla_generalized_eigenvalues(3)
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NAME

6       elpa_generalized_eigenvalues - computes the eigenvalues of a
7       generalized eigenvalue problem for real symmetric or complex hermitian
8       matrices
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SYNOPSIS

12   FORTRAN INTERFACE
13       use elpa
14       class(elpa_t), pointer :: elpa
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16       call elpa%generalized_eigenvalues (a, b, ev, is_already_decomopsed,
17       error)
18
19       With the definitions of the input and output variables:
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21       class(elpa_t) :: elpa  ! returns an instance of the ELPA object
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23       datatype :: a
24              The matrix a for which the eigenvalues should be computed. The
25              dimensions of matrix a must be set BEFORE with the methods
26              elpa_set(3) and elpa_setup(3). The datatype of the matrix can be
27              one of "real(kind=c_double)", "real(kind=c_float)",
28              "complex(kind=c_double)", or "complex(kind=c_float)"
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30       datatype :: b
31              The matrix b defining the generalized eigenvalue problem. The
32              dimensions and datatype of the matrix b has to be the same as
33              for matrix a.
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35       datatype :: ev
36              The vector ev where the eigenvalues will be stored in ascending
37              order. The datatype of the vector ev can be either
38              "real(kind=c_double)", or "real(kind=c_float)", depending of the
39              datatype of the matrix. Note that complex hermitian matrices
40              also have real valued eigenvalues.
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42       logical :: is_already_decomposed
43              Has to be set to .false. for the first call with a given b and
44              .true. for each subsequent call with the same b, since b then
45              already contains decomposition and thus the decomposing step is
46              skipped.
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49       integer, optional :: error
50              The return error code of the function. Should be "ELPA_OK". The
51              error code can be querried with the function elpa_strerr(3)
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54   C INTERFACE
55       #include <elpa/elpa.h>
56       elpa_t handle;
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58       void elpa_generalized_eigenvalues(elpa_t handle, datatype *a, datatype
59       *b, datatype *ev, int is_already_decomposed, int *error);
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61       With the definitions of the input and output variables:
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64       elpa_t handle;
65              The handle to the ELPA object
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67       datatype *a;
68              The matrix a for which the eigenvalues should be computed. The
69              dimensions of the matrix must be set BEFORE with the methods
70              elpa_set(3) and elpa_setup(3). The datatype can be one of
71              "double", "float", "double complex", or "float complex".
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73       datatype *b;
74              The matrix b defining the generalized eigenvalue problem. The
75              dimensions and the datatype of the matrix b must be the same as
76              matrix a.
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78       datatype *ev;
79              The storage for the computed eigenvalues. Eigenvalues will be
80              stored in ascendig order. The datatype can be either "double" or
81              "float". Note that the eigenvalues of complex hermitian matrices
82              are also real.
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84       int is_already_decomposed;
85              Has to be set to 0 for the first call with a given b and 1 for
86              each subsequent call with the same b, since b then already
87              contains decomposition and thus the decomposing step is skipped.
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89       int *error;
90              The error code of the function. Should be "ELPA_OK". The error
91              codes can be querried with elpa_strerr(3)
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DESCRIPTION

95       Compute the generalized eigenvalues and (parts of) the eigenvector
96       spectrum of a real symmtric or complex hermitian matrix.The functions
97       elpa_init(3), elpa_allocate(3), elpa_set(3), and elpa_setup(3) must be
98       called BEFORE elpa_generalized_eigenvalues can be called. Especially
99       the number of eigenvectors to be computed can be set with elpa_set(3).
100       Unlike in the case of ordinary eigenvalue problem, the generalized
101       problem calls some external scalapack routines. The user is responsible
102       for initialization of the blacs context, which then has to be passed to
103       elpa by elpa_set(3) BEFORE elpa_generalized_eigenvalues can be called.
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NAME

SYNOPSIS

DESCRIPTION

SEE ALSO